The present invention relates to subterranean fracturing operations, and more particularly to fracturing fluids comprising an improved fluid loss control additive, and methods of using such fracturing fluids in fracturing subterranean formations.
Hydrocarbon-producing wells are often stimulated by hydraulic fracturing operations, wherein a viscous fracturing fluid is introduced into a hydrocarbon-producing zone within a subterranean formation at a hydraulic pressure sufficient to create or enhance at least one fracture therein. Generally, the fracturing fluid suspends proppant particles that are to be placed in the fractures to prevent the fractures from fully closing (once the hydraulic pressure is released), thereby forming conductive channels within the formation through which hydrocarbons can flow. Once at least one fracture is created and at least a portion of the proppant is substantially in place, the viscosity of the fracturing fluid may be reduced, to be removed from the formation.
In certain circumstances, a portion of the fracturing fluid may be lost during the fracturing operation, e.g., through undesirable leakoff into natural fractures present in the formation. This is problematic because such natural fractures often have higher stresses than fractures created by a fracturing operation. These higher stresses may damage the proppant and cause it to form an impermeable plug in the natural fractures, that may prevent hydrocarbons from flowing through the natural fractures.
Conventionally, operators have attempted to solve this problem by including a fluid loss control additive in the fracturing fluid. Conventional fluid loss control additives generally comprise rigid particles having a spheroid shape. The use of these additives can be problematic, inter alia, because such additives may require particles that have a distinct particle size distribution to achieve efficient fluid loss control. For example, when such additives are used to block the pore throats in the formation, a sufficient portion of relatively large particles will be required to obstruct the majority of the pore throat, and a sufficient portion of relatively small particles will also be required to obstruct the interstices between the large particles. Furthermore, for certain conventional fluid loss control additives, such a desired particle size distribution may be difficult to obtain without incurring the added expense of reprocessing the materials, for example, by cryogenically grinding them to achieve the desired particle size distribution.